<?php 

$arr = [

'2:40:15',
'2:53:20',
'2:56:32',
'2:59:25',
'3:51:45',
'4:03:38',
'4:18:24',
'4:25:39',
'4:32:48',
'4:34:09',
'4:35:08',
'4:45:41',
'5:01:32',
'5:09:22',

];

foreach($arr as $v) {
	$a = explode(':', $v);
	echo $a[0]*60*60+$a[1]*60+$a[2] . PHP_EOL;
}